//一个map的实现
//http://dh189.iteye.com/blog/724632

function Map(linkItems) 
{   
    this.current = undefined;   
    this._size = 0;   
    if(linkItems === false)
	{  
        this.disableLinking();   
    }   
}  

/** 
 * 获取当前map 
 * @return 当前对象 
 */  
Map.noop = function() 
{   
    return this;   
};   

/** 
 * 非法操作 
 * @return 
 */  
Map.illegal = function() 
{
    throw new Error("非法操作，Map已经被禁用");   
};   
/** 
 *  
 * @param obj 
 * @param foreignKeys 
 * @return 
 */  
Map.from = function(obj, foreignKeys) 
{
    var map = new Map;   
    for(var prop in obj) 
	{
        if(foreignKeys || obj.hasOwnProperty(prop))
		{
            map.put(prop, obj[prop]);   
        }   
    }   
    return map;   
};   

// 禁用map  
Map.prototype.disableLinking = function() 
{
    this.link = Map.noop;   
    this.unlink = Map.noop;   
    this.disableLinking = Map.noop;   
    this.next = Map.illegal;   
    this.key = Map.illegal;   
    this.value = Map.illegal;   
    this.clear = Map.illegal;   
    return this;   
};   

/** 
 * 返回hash值 例如：number 123 
 * @param value key/value 
 * @return 
 */  
Map.prototype.hash = function(value) 
{
    return	(typeof value) + ' ' + (value instanceof Object ? 
			(value.__hash || (value.__hash = ++arguments.callee.current)) : 
			value.toString());  
};   
  
Map.prototype.size = function() 
{
    return this._size;  
};   
  
Map.prototype.hash.current = 0;   

Map.prototype.get = function(key) 
{
    var item = this[this.hash(key)];   
    return item === undefined ? undefined : item.value;   
};   

Map.prototype.put = function(key, value) 
{
    var hash = this.hash(key);   
    if(this[hash] === undefined) 
	{
        var item = { key : key, value : value };   
        this[hash] = item;   
        this.link(item);   
        ++this._size;   
    }
	else
	{  
        this[hash].value = value;  
    }   
    return this;   
};  

Map.prototype.remove = function(key) 
{
    var hash = this.hash(key);   
    var item = this[hash];   
    if(item !== undefined) 
	{
        --this._size;   
        this.unlink(item);   
        delete this[hash];   
    }   
    return this;   
};  

/** 
 * 清除map 
 * @return 
 */  
Map.prototype.clear = function() 
{
    while(this._size)
	{  
        this.remove(this.key());   
    }   
    return this;   
};  

/** 
 * 处理队列 
 * @param item 
 * @return 
 */  
Map.prototype.link = function(item) 
{
    if(this._size == 0) 
	{
        item.prev = item;   
        item.next = item;   
        this.current = item;   
    }
	else 
	{   
        item.prev = this.current.prev;   
        item.prev.next = item;   
        item.next = this.current;   
        this.current.prev = item;  
    }   
};  

Map.prototype.unlink = function(item) 
{
    if(this._size == 0)
	{
        this.current = undefined;  
    }
	else 
	{   
        item.prev.next = item.next;   
        item.next.prev = item.prev;   
        if(item === this.current)
		{
            this.current = item.next;   
        }   
    }   
};   

/** 
 * 获取下一个 
 * @return 
 */  
Map.prototype.next = function() 
{
    this.current = this.current.next;   
    return this;  
};   

/** 
 * 获取key 
 * @return 
 */  
Map.prototype.key = function() 
{
    return this.current.key;   
};   

/** 
 * 获取value 
 * @return 
 */  
Map.prototype.value = function() 
{
    return this.current.value;   
}; 

exports.Map = new Map();